SDRAM vs. ECC SDRAM vs. ECC SDRAM REG.

Hi there,

what is exactly the difference between SDRAM and SDRAM with ECC ? And are there any differences between ECC SDRAM and REGISTERED ECC SDRAM or is it the same ? If I build a P4 Server system based on PC133 SDRAM, is it recommendable to use the ECC Memory ???

Thanks,

M. Zehr